Conventionally, in the field of paper making, various papermaking chemicals such as the following have been known: for example, agents for retention and drainage for improvement in retention and drainage of raw material pulp and/or filler so that operability and working efficiency can be improved; and for example, a paper strength agent for improvement in strength of paper products.
For such papermaking chemicals, a paper strength agent composed of an aqueous solution of an acrylamide-based polymer has been known, and to be specific, Patent Document 1 below has proposed, for example, that a paper strength agent is produced as an aqueous solution of an amphoteric polyacrylamide by introducing acrylamide, dimethylaminoethylmethacrylate, a quaternary compound of dimethylaminoethylmethacrylate, itaconic acid, sodium methallylsulfate, methylenebisacrylamide (polyfunctional vinyl monomer), and ion-exchange water, and adding a polymerization initiator (ammonium persulfate) to be reacted.